The present invention relates to a rotor of a charging dynamoelectric machine which is driven by a vehicle or marine engine and which supplies electric power to a battery and electrically operated equipment.
A conventional charging dynamoelectric machine is shown in FIG. 1.
In FIG. 1, reference numeral 1 designates a rotor which is composed of a pair of jaw-type magnetic poles 2, a field winding frame 3 around which a field winding 4 is wound, a rotary shaft 5, and slip rings 6. The field winding frame 3 is held between the pair of magnetic poles 2 by press fitting the rotary shaft 5 thereinto. Stators 7 is disposed around the magnetic poles 2 with small clearances therebetween. Reference numeral 8 indicates a brush holder on which a voltage controller is mounted. Reference numeral 9 indicates a rectifier. A driven pulley 10 and fan 11 are integrally fixed to the rotary shaft 5 respectively. Reference numerals 12 and 13 indicate brackets, and numerals 14 and 15 indicate bearings for rotatably supporting the rotor 1.
FIG. 2 is a fragmentary enlarged view showing the magnetic poles 2 and the field winding frame 3 included in the rotor 1. In FIG. 2, a plurality of pole teeth 22 extend from the yokes 21 of the poles 2. Reference numeral 3a indicates exterior surfaces of the field winding frame 3. Interior surfaces of the base portions 21a of the yokes 21 and the exterior surfaces 3a of the field winding frame extend parallel to one another.
The operation of the conventional charging dynamoelectric machine will now be explained. A field current is supplied via the brush holders 8 and slip rings 6 to the field winding 4. At the same time, the pulley 10 is driven by a belt. Accordingly, the stators 7 generate an alternating current. This alternating current is converted by the rectifier 9 to a direct current, which forms the output of the generator.
During the period of time when the dynamoelectric machine is actuated, a magnetic attractive force is applied to the magnetic poles 2 due to the magnetic flux in the gaps between the magnetic poles 2 and the stators 7. This magnetic flux changes continuously with time so that the magnetic attractive force acts as oscillating force on the magnetic poles 2 in a manner as shown by arrows in FIG. 2. This oscillation produces so-called "electromagnetic sound", constituting a detrimental property of the machine.